Stadium or bleacher seating has in the past been made in the form of benches or chairs utilizing wooden planks or slats. Wooden seating suffers a disadvantage since as the world's supply of wood has become more in demand for other uses, such as furniture, paper, etc., it has become impractical to continue fabricating large numbers of stadium seats from wood. Furthermore, stadium seats are generally fabricated in such a manner as to be relatively inexpensive, and so, as anyone who has attended many events held in a stadium readily discovers, backrests are generally not available. Wooden backrests, in addition to being expensive to manufacture, are impossible to fabricate with a comfortable contour because of the inherent rigidity of the material. As a result, stadium seats are generally constructed in a continuous fashion with an uncomfortable flat seating surface and generally without backrests.
Wooden components have also always suffered the inherent disadvantage of being subject to deterioration from weathering and the attendant high cost of maintenance. Some attempt has been made to substitute aluminum to obviate this difficulty. However, aluminum transmits temperature differentials to the spectator making the seat uncomfortable. Aluminum seating also lacks comfort gained by compound curve contour available in plastic seating.
The modular seating concept for spectator seating wherein individually contoured seats of molded plastic material are assembled in juxtaposition on a metal substructure has now gained wide acceptance since it overcomes the shortcomings of both wood and aluminum. Modular seating units can be installed on steel or concrete substructures. The modular seats are also used on telescoping and portable units. Because they combine aluminum substructures and high density polyethylene seat modules, they are not only extremely durable, but also light in weight, further adding to their desirability.
The basic patent, illustrating this broad concept is U.S. Pat. No. 3,702,204, issued Nov. 7, 1972. I am a co-inventor of this basic patent.
Early in the marketing effort of the basic bleacher seat, it was recognized that there was a need for backrests for new installations. Further, updating current structures by adding back supports to modular seating makes an older facility new looking and can increase spectator attendance figures by offering the extra comfort.
In prior art chair frame structures of which I am aware, and in my first attempt at adding a back to the modular seat, the backrest members are joined in pairs with the edges of the members being simply secured by nuts and bolts. The presence of holes in the joined parts has been found to weaken the edges of the seat back and after continuous use, the fasteners passing through the seat backs tend to enlarge the hole causing the assembly to become loose. In addition, the location of the features, in close proximity to the backrest, made it difficult to reach with a screwdriver or other tool to tighten during initial installation.
In developing refinements and improvements to my initial attempt, it was thus important to me to provide a simplified structure or assembly that is permanent and secure, i.e., without parts that could become loose. The assembly had to be capable of accommodating the differential expansion due to thermal variations, as well as mechanical vibrations, and rough use normally found at sports events. The backs and the supports should be capable of withstanding relatively high loads which occur when sports fans improperly use the backrest as a footrest. My work in this direction has led to the present invention.